I was on my local drum shops website and I came across "Warm up aids"
I clicked it and I find something called a Gyroball (or powerball).
I looked at videos and all I really seen were guys with muscles spinning they're wrists with a ball in the hand.

What does it actually do?
It's supposed to be good for your wrist muscles I think.

It sure beats squeezing a tennis ball! That was the therapy that my doctors gave me until I showed them drumming.

Hahaha! Squeezing a tennis ball, I heard squeezing oranges is also another solution. But this ball thing seems really cool! And not only does it help your health but also strenghtens hand muscles and helps your drumming :)